Everything that wheezes is NOT asthma. Today we look at three of the major diagnoses in the wheezing child: Asthma, Croup and Bronchiolitis. Probably the diagnoses that cause greatest overlap and confusion are bronchiolitis and asthma.
Dr Claire Watkins gave a great talk at EMCORE 2017, which you can watch below. Here are some of the most important points coming from that talk.
Bronchiolitis is caused by inflammation of the bronchioles secondary to a viral illness. The result is wheeze due to airway smooth muscle spasm and increased airway mucus hypersecretions, that result in the crepitatations often heard.
We tend to think of bronchiolitis as occurring in those children under one year of age and asthma occurring in those greater than two years of age. This leaves an area of uncertainty in those between one and two years of age. Let’s change that thinking. Asthma predominantly occurs in this children greater than two years old and bronchiolitis in those children less than two years old.
We judge severity from the vitals, such as respiratory rate and saturations and the work of breathing. Below is a chart from the Royal Children’s Hospital Melbourne.
Should we give Antibiotics? NO
Should we give Steroids? NO
Should we give Salbutamol? NO
Do not give antibiotics. This is a virus. It’s rare for this group of patients to get a secondary bacterial infection.
There is NO evidence that steroids have a place in bronchiolitis. They have no effect on the symptoms and they do not reduce the admission rate.
The argument for salbutamol is that it works on airway smooth muscle and as such may help. The arguments against the use of salbutamol are:
- Smooth muscle in the airways develops until the child is about 8 years old. In the very young there is a variable amount, but overall not much of the smooth muscle development and the use of a beta 2 agonist has variable effect.
- The use of salbutamol is not without toxicity. Salbutamol toxicity results in tachycardia, tachypnoea, tremor, ventilation/perfusion mismatch(lower sats on the treatment), hypokalaemia and a potentially significant lactic acidosis
Why does the Ventilation Perfusion mismatch occur?
The use of salbutamol, especially on air, results in a pulmonary vasodilatation, which means that there is more blood flow, however this flow occurs to all alveoli, even the ones not being ventilated, thus the drop in oxygen saturations.
Lactic acidosis can have a profound effect on these children and can make them look even sicker and may even result in more salbutamol being given.
What do we do?
Minimal handling is perhaps the best approach. Perhaps add oxygen. High flow nasal prongs(2L/kg) and low flow nasal prongs are possible. Keep them calm and sit them up. Feeding support is also important, nasogastric feeding is better than intravenously.
Asthma is a small airways disease secondary to a viral illness or an allergen. It results in wheeze due to airway smooth muscle spasm and increased airway mucus hypersecretion.
Treating the asthma patient does require salbutamol, and although lactic acidosis is still a potential issue, it works. The way to avoid severe lactic acidosis is to not use continuous nebulisers, but to use burst therapy i.e., if less than 6 years old, 6 puffs, if older than 6, 12 puffs, twenty minutes apart, three doses.
Steroids are an important part of the treatment of severe asthma. However there is now a movement to not give steroids to the pre-school age groups( 2-5 years old) as it can affect growth and skeletal development. However steroids should be given in the unwell asthmatic i.e.., those that are being admitted and those that require other treatment.
What about the child with the silent chest?
The child with the true silent chest has a MARKED increased work of breathing and may be drowsy or have a tachycardia, or bradypnoea. The child that is not working very hard, but just not taking deep breaths, is probably not a silent chest.
Croup is a viral infection of the upper airways and is associated with an upper airway obstruction and marked increased work of breathing.
Think of the potential differentials in the child with croup. Think of epiglottis, and bacterial tracheitis as two more important differentials. This is more so as we start to see immunisation rates drop.
Below is the assessment of severity for a patient with croup, as set out in the Royal Children’s Hospital Clinical Guidelines.
In most cases these children will present with a mild form of croup, i.e., with only a barking cough and perhaps some stridor when upset. The other side of the severity range will include children with marked stridor at rest, much increased work of breathing and even hypoxaemia.
There is an argument for not treating the simple presentation of a child with a barking cough. However there must contingencies in place, in case the child gets worst. Parents need to be well advised to represent.
Certainly any child with stridor at rest and increased work of breathing needs steroids.
There is no role for antibiotics.
Adrenaline may buy some time, whilst the child improves, by causing vasoconstriction and decreasing oedema in the airway, however, it does not treat the condition.
Steroids decrease the hospital stay, need for adrenaline and need for intubation. Dexamethazone 0.6mg/kg(12mg maximum) can be given orally(preferred) or IM. Give it early.